Pulse Width Modulation Control Signal Research Articles

Design and implementation of pulse width modulation gate control signals for two-level three-phase inverters

The switching control circuit in a DC to AC inverter is the critical part that is applied to control the power transistors insulated-gate bipolar transistor (IGBTs) and metal-oxide semiconductor field-effect transistor (MOSFETs). This paper proposes a high-performance and low-cost pulse width modulation (PWM) control signal with a 120º phase shift circuit for a two-level three-phase inverter. Typically, a PWM signal with a 120º phase shift for three-phase inverters is generated with the help of analogue components with more complicated designs and power losses or by using a microcontroller with necessary programming or coding. The proposed solution is to design a 120° three-phase shift circuit based on D flip-flops and the 555-timer to generate the clock signal for the flip-flop input in addition to the dead-time control circuit. The proposed circuit is controlled by one square wave signal as an input signal to generate six output PWM control signals at 50 Hz to operate six MOSFETs in the three-phase inverter. Simulation results in power simulation software PSIM and PROTEUS simulation tools are used to verify the proposed circuit. Hardware implementation of the proposed circuit and three-phase inverter is carried out to validate the performance of the proposed design.

Decentralized space vector pulse width modulation method for multilevel single-phase half bridge converters

This study presents a space vector pulse width modulation (PWM) method for a multilevel single-phase decentralized power converter (DPC) called MSPDPC. The proposed model is built by connecting half-bridge cells in series. The output voltage can be adjusted according to demand by adding or subtracting cells. Cells use communication protocols to transmit and receive information with two neighboring cells. The received data contains information for the decentralized space vector pulse width modulation (DSVPWM) method proposed in this paper. In the proposed DSVPWM method, cells set up links to exchange information such as cell position, total cells in a phase, reference voltage amplitude, and reference frequency. The PWM control signals of each cell are calculated based on the information received. The study also focuses on evaluating the ability to adjust the switching vector and the corresponding dwell time of the cells when the structure of the DPC changes. The ability to dynamically reconfigure the DPC is a crucial feature that ensures uninterrupted power supply in case of one or several cell failures. The system automatically establishes a new state with the active cells. The proposed configuration and communication method between cells provide very fast configuration times. The load voltage of the DPC is adjusted to 0.5 times the voltage per cell, which allows the modulation voltage amplitude to be adjusted best according to the load requirements. The study used Matlab/Simulink software to review the initial assessments. The proposed model and algorithms will be verified on the Digital Signal Processor (DSP) platform with a 220V/500W load.

Distributed output agreement of PWM‐controlled double‐integrator multi‐agent systems with switching topologies

This paper studies the distributed pulse-width-modulation (PWM) control problem for double-integrator multi-agent systems with switching topologies. Usually, a PWM control signal updates only on discrete-time sample instants and only takes three constant values. This means that the methods based on linear and continuous designs are not directly applicable. The major contribution of this paper is that a new class of distributed PWM controllers, which feature nested saturated loops, is proposed. With the new design, the outputs of the controlled agents asymptotically converge to each other, as long as a mild connectivity condition is satisfied. The validity of the proposed PWM controller is proved based on a new invariant-set-like method. This work first shows that the state of each PWM-controlled agent stays within an appropriately chosen closed set if the interactions are bounded. Then, under a mild connectivity condition, the state boundedness and convergence of the closed-loop multi-agent system by analyzing the boundedness of the interactions are proved. A numerical example is employed to verify the effectiveness of the proposed design.

Hybrid soft switching DC–DC boost converter

AbstractIn this study, hybrid soft switching (HSS) DC–DC boost converter is proposed. The proposed converter operates as the conventional discontinuous conduction mode (DCM) pulse‐width modulated (PWM) DC–DC boost converter at light loads. When the output power increases, the snubber cell is activated, and the converter operates as frequency controlled soft switching resonant converter. Thus, higher efficiency is obtained at high power levels. In the proposed converter, the snubber cell works with a simple on–off logic instead of PWM control. Thus, it has a quite simple structure consisting of only a switch and a snubber capacitor, and does not need an additional PWM control signal. Hence, the proposed converter has the advantages of conventional DCM PWM converters while operating with higher efficiency at higher power levels. There is no additional voltage stress on any semiconductor power devices. Theoretical analysis is verified with a laboratory application of a DC‐DC boost converter having input voltage of 90 V, output voltage of 400 V and output power of 1 kW.

Matching Resonant Switches Operation Using Classical Pulse-Width Modulation Algorithms

This paper presents a new method of controlling resonant switches of a converter, in which the instants of control pulses supply to the main and auxiliary switches of the circuit are strictly synchronized with pulse-width modulation (PWM) logic signals. Any classical options providing the specified quality of the output voltage and current can be used as such signals. The control pulses durations of the main switches have the same time intervals as those of the PWM control signals, since the control pulses are shifted relative to the PWM signals by a constant time delay. The durations of control pulses of auxiliary switches used to activate resonant switching processes are constant and independent of changes of the electric mode parameters of the circuit and the scatter of the parameters of resonant circuit components. The synchronizing mode is shown to be achieved by introducing two additional time intervals into each resonant switching cycle compensating the effect of external and internal factors on the duration of the required control pulses for the main and auxiliary switches of the converter. Such additional time intervals are the duration of free—that is, without significant loss of power—circulation of current (energy) in the inductance of the resonant circuit. In addition, it is shown that the necessary conditions for free circulation are the capability of the main converter switches for bilateral current conductivity and the absence of energy absorption sources in the circulation circuit. The diagrams are presented of switching processes demonstrating the advantages of a new method for controlling resonant switches of the inverter in a wide range of the supply voltage and load current variations of the circuit.

Fast Switching Valve Utilization to Control Pneumatic Cylinder Speed

The position and speed of the piston of pneumatic cylinder are very important parameters in evaluating the pneumatic system performance. Utilization of Pulse Width Modulation (PWM) technique to control the Fast Switching Valve (FSV) usually causes fluctuation in the piston motion and accordingly, the system performance deteriorates. The objective of this work is to introduce a novel PWM control technique considering the suitable duty cycles according to the switching frequency in order to improve the FSV characteristics and reduce piston speed fluctuation. A test rig for a simple pneumatic circuit with an FSV as a control element has been designed and realized. The displacement of the piston is measured using a Linear Wire Potentiometer Transducer (LWPT), while its derivative is used to estimate the speed considering a low pass filter to reduce the effect of piston position signal noise. A nonlinear mathematical model is introduced and experimentally validated. The results of both computer simulation and experimental measurements show that the integration between fast switching valve and PWM control signal leads to a quasi-linear relationship between duty cycle and piston speed. Moreover; results proved the successful control of piston speed based on the correct duty cycle and valve switching frequency.

Novel Bipolar-Type Direct AC–AC Converter Topology Based on Non-Differential AC Choppers

This paper introduces a novel H-bridge structured ac–ac pulsewidth modulation (PWM) converter topology based on two-level non-differential ac chopper legs, which can work at the non-inverting and inverting modes for the utility voltage compensation. Compared to the traditional bipolar-type H-bridge ac–ac converter, no bidirectional switches are switched in a complementary manner to overcome the commutation problem due to the delayed response of electronic circuits and semiconductor switching devices. The detailed PWM control signals and operational principles are presented to regulate the output voltage in a bipolar manner. Especially the main advantage is that the proposed ac–ac converter has the same buck/boost operation process for non-inverting and inverting modes, which ensures the continuously average current supply to the low-voltage output side without a high-value capacitor to support power. Additionally, due to the common sharing ground of the input and output, the feature that output can reverse or maintain phase angle with input is supported well. Then, the detailed analysis, design conditions, and experimental verification based on a 1 kW experimental prototype are presented.

Performance Analysis of Modular Forward Converter in Input Parallel Output Series (IPOS) Architecture Using PI and Fuzzy Logic Controller

This paper investigates the performance of modular dc–dc forward converter in Input Parallel Output Series (IPOS) configuration which is controlled by an effective controller. This IPOS topology facilitates the converter to have high output voltage gain. The role of controller is crucial in ensuring the power sharing between the converters. Fuzzy controller, known for its versatility, is employed in this research work. The fuzzy controller feeds appropriate pulse width modulated control signals for appropriate input and load regulation. The performance of the fuzzy controller is analyzed by comparing it with proportional integral controller and a advanced neural network controller. The proposed IPOS system has been analyzed using MATLAB/Simulink environment and hardware prototype. The simulation and hardware results reveal that the suggested topology with fuzzy controller is very effective compared to its counterparts.

An Energy Saving Variable Damping Seat Suspension System With Regeneration Capability

In this paper, an energy saving variable damping seat suspension system is designed, manufactured, modeled, and validated. A continuously controllable electromagnetic damper (EMD) system, which consists of a permanent magnet synchronous motor, a three-phase rectifier, a metal–oxide–semiconductor field-effect transistor (MOSFET) switch, and an external resistor, is built and tested first. Its model parameters have been identified based on the test results. The EMD's damping property can be controlled by exerting pulsewidth modulation (PWM) signal with different duty cycles on the MOSFET switch. The EMD is integrated with a planetary gearbox to amplify its torque output, and the formed variable damper is installed on the center of the scissors structure of a seat suspension. By analyzing the EMD test results and the seat suspension's kinematic, the controllable damping of the proposed seat suspension is derived as 112 to 746 N·s/m. A control method for vibration isolation is proposed based on the system model. The proposed variable damping seat suspension and its controller are validated on a six-degrees-of-freedom vibration platform in both frequency domain and time domain; a well-tuned commercial passive seat suspension is also tested for comparison. The test results show that the controlled variable damping seat suspension has better performance in vibration isolation than the proposed seat with highest and lowest damping, and the conventional passive one. In the meantime, the RMS value of the system harvestable power is 1.492 W, and the power consumption of the PWM control signal is small. Therefore, this variable damping seat suspension can improve ride comfort with ignorable energy cost.

A Nonintrusive Diagnostic Method for Open-Circuit Faults of Locomotive Inverters Based on Output Current Trajectory

Open-circuit (OC) fault diagnosis of voltage source inverters on trains still has two problems to be improved. First, it is usually forbidden to change the system structures of trains or to add any extra sensor. Therefore, diagnostic methods which need pulse width modulation control signals or extra output voltage sensors are no longer suitable for trains. Second, loads on the train vary in a wide range and have significant influence on output currents. In order to solve these problems and increase the maintenance efficiency, an online diagnostic method for single switch OC (SSOC) faults and double switches OC (DSOC) faults is proposed. Supposing that three phases are balanced, it is proved that the trajectory of two output currents is an ellipse in the Cartesian coordination, and each OC fault has a unique trajectory. SSOC faults and DSOC faults can be isolated by detecting abnormal slopes and directions of several consecutive points on the trajectory. The fastest diagnostic process takes less than half a period. Load variation has impact on the size and shape of the trajectory but does not affect the diagnostic method. Experimental tests are carried out on dSPACE platform. Results show the accuracy of the mathematical model and the effectiveness of the online diagnostic method proposed in this paper.

Study on control performance of pilot high-speed switching valve

High-speed switching valves have been widely studied as pilot valves because of their advantages on easy digital control, low power loss, and non-sensitive to oil pollution. However, there are still lots of difficulties and problems between discrete flow and response time. In this article, two high-speed switching valves are used to pilot a three-way main stage valve. By adjusting the duty ratio of pulse width modulation control signals, the main stage can output continuous flow and pressure. The control performances of two pilot stage methods, which are high-speed switching valve and proportional valve, are compared through the theoretical analysis and the dynamic simulation. It is found that three factors directly affect the response time of the main stage, which are the control signal, the operating frequency of high-speed switching valve, and the pressure of the control chamber. The main valve can achieve better performance if optimized parameters are applied.

Effects of Operating Parameters for Dynamic PWM Variable Spray System on Spray Distribution Uniformity

Abstract: A dynamic PWM (Pulse Width Modulation) variable spray experiment platform was built up to study the spray distribution characteristics of PWM spray progress. The homogeneity of single nozzle dynamic spraying was evaluated based on this platform under different experiment condition. Carmine solution concentration-absorbance technology was adopted to get the CV (Coefficient of Variation) value of percent area spray coverage. RSM (Response Surface Methodology) with three variables including frequency, duty cycle of PWM control signal and forward velocity of spray was employed to study the effects of these three factors on dynamic spray distribution uniformity. Compared with previous common study of static spraying, the research on this paper can evaluate the actual spray distribution uniformity of dynamic spraying more accurately. Moreover, the platform and the research method can provide references for the settings of PWM variable-rate spray operation parameters in practical plant protection work.

Autotuning of Digital Deadbeat Current Controllers for Grid-Tie Inverters Using Wide Bandwidth Impedance Identification

By injecting a wide-bandwidth small-amplitude test sequence into the inverter's pulsewidth-modulated control signal and by utilizing digital network analyzer techniques, an accurate estimation of the inverter's output inductance can be obtained without external equipment and under realistic operating conditions, which is important given the nonlinear characteristics of commonly used powdered iron cores. This knowledge can be then leveraged to tune the inverter's digital deadbeat controller for optimal performance, i.e., reaching the desired reference in n switching cycles, where n is the order of the system. A pseudorandom-binary-sequence-based injection sequence is chosen for its wideband spectral content. Experimental results demonstrate the improvement in the output-current total harmonic distortion obtainable with the proposed approach.

Wireless PWM Control of a Parallel DC–DC Buck Converter

We demonstrate a new concept for wireless pulse-width modulation (PWM) control of a parallel dc-dc buck converter. It eliminates the need for multiple physical connections of gating/PWM signals among the distributed converter modules. The new scheme relies on radio-frequency (RF) based communication of the PWM control signals from a master to the slave modules. We analyze the system stability and demonstrate the experimental effectiveness of the wireless control scheme for a two-module parallel buck converter for 10-kHz and 20-kHz switching frequencies and for channel lengths of 1.5 and 15ft, respectively. The proposed control concept may lead to easier distributed control implementation of parallel dc-dc converters and distributed power systems, and may lead to redundancy that is achievable using droop method. It may also be used as a backup for wire-based control of parallel converters to provide fault tolerance.

Pulse-Width-Modulation control of some mechanical systems

Pulse-Width-Modulation (PWM) control strategies have been of limited interest, and use, in the regulation of a large class of mechanical systems, such as robotic manipulators and rigid spacecrafts. The chattering associated to discontinuous bang-bang feedback control input signals has traditionally posed serious concerns when considering the selection of this robust and efficient control technique over some other smooth control alternatives. This article proposes a means of circumventing the inconveniences caused by the PWM control signal discontinuities in such a class of systems, while retaining the robust features of the PWM control approach.